Much of math intuitively chains from other math. With interest and some smarts a kid can easily be that far ahead in the early years. Without instruction or intentional pursuit that gap can narrow as algebra and some other topics aren't quite as intuitive. My DS8 is in that range on math, and makes hs own effort to keep extending his knowledge and has maintained it by teaching himself algebra through various resources.
He was in an immersion program (ours is called learning immersion, guessing yours is a language one?) and just missed on a rubric in first grade to go to an HG program for second. The solution for him was skipping second to get into the gifted program (full time classroom) that started in 3rd. It's been working well.
Bored is an unnatural state for kids.
